Device and method for constantly adjusting the concentration and filling level of developing solution in a printing process

Abstract

A liquid developing device comprises a storage tank, a concentration sensor, a level sensor, a concentrated-ink supply pump, a carrier supply pump, an ink discharge pump, and a controller. The storage tank stores ink, including toner and carrier, for developing a photoconductor. The concentration sensor measures a concentration of ink to be supplied to the photoconductor. The level sensor measures the amount of ink stored in the storage tank. The concentrated-ink supply pump sends concentrated ink to the storage tank. The carrier supply pump sends carrier to the storage tank. The ink discharge pump discharges excessive ink from the storage tank. Based on measurement value and amount from the concentration tank and the level sensor, the controller controlls the concentrated-ink supply pump, the carrier supply pump, and the ink discharge pump, so that the concentration and amount of ink stored in the storage tank is retained at a predetermined level.

What is claimed is:  
     
       1. A liquid developing device comprising: 
       a storage tank which stores an ink, including a toner and a carrier, for developing an electrostatic latent image formed on a photoconductor;  
       an ink supply pump which sends an ink from said storage tank to the photoconductor;  
       a concentration sensor which measures a toner concentration of the ink to be sent to the photoconductor;  
       a storage-amount sensor which measures an amount of ink stored in said storage tank;  
       a concentrated-ink supply pump which sends a concentrated ink from an ink cartridge for storing an concentrated ink to said storage tank;  
       a carrier supply pump which sends a carrier from a carrier cartridge for storing a carrier to said storage tank;  
       an ink discharge pump which discharges excessive ink from said storage tank to a discharge cartridge; and  
       a controller which includes a control mode that simultaneously controls and drives said concentrated-ink supply pump, said carrier supply pump, and said ink discharge pump, so as to maintain a predetermined level of the toner concentration of the ink stored in said storage tank and a predetermined amount of the ink, based on a measurement value from said concentration sensor and a measurement amount from said storage-amount sensor; wherein  
       said controller supplements said storage tank with a concentrated ink using said concentrated-ink supply pump, supplements said storage tank with a carrier using said carrier supply pump, and discharges an excessive ink from said storage tank using said ink discharge pump, based on an error between a measurement value from said concentration sensor and a predetermined value of the concentration and an error between a measurement amount from said storage-amount sensor and a predetermined amount, so that the toner concentration of the ink stored in said storage tank and the amount of the ink approach the predetermined value of the concentration and the predetermined amount, respectively.  
     
     
       2. The liquid developing device according to  claim 1 , wherein said controller drives each of said concentrated-ink supply pump, said carrier supply pump, said ink discharge pump, so as to supply a concentrated ink or a carrier to said storage tank, in accordance with at least one of the error between the measurement value from said concentration sensor and the predetermined value of the toner concentration, an integrated result of the error, and a differentiated result of the error, and to supply a concentrated ink and a carrier to said storage tank or to discharge an excessive ink from said storage tank, in accordance with at least one of the error between the measurement amount from said level sensor and the predetermined amount, an integrated result of the error, and a differentiated result of the error. 
     
     
       3. A liquid developing device comprising: 
       four storage tanks which respectively store four colors, yellow, cyan, magenta, and black, of inks, each including a toner and a carrier, for use in developing an electrostatic latent image formed on a photoconductor;  
       four ink supply pumps which respectively send the four colors of inks from the respective storage tanks;  
       four concentration sensors which respectively measure toner concentrations of the respective four colors of inks to be sent to said photoconductor;  
       four storage-amount sensors which respectively measure amounts of four colors of inks stored in the respective storage tanks;  
       four concentrated-ink supply pumps which respectively send four colors of inks from ink cartridges to the respective storage tanks each of which stores a same color of ink as a color of a concentrated ink stored in one of four ink cartridges;  
       a carrier supply pump which sends a carrier to the storage tanks from a carrier cartridge storing a carrier;  
       four ink discharge pumps which respectively discharge excessive inks from the respective storage tanks to a discharge cartridge; and  
       a controller which includes a control mode that simultaneously controls and drives each of said concentrated-ink supply pumps, said carrier supply pump, and said ink discharge pumps, so as to maintain a predetermined level of the toner concentrations of the inks stored in the respective storage tanks and a predetermined amount of the inks stored therein, based on a measurement value from each of said concentration sensors and a measurement amount of each of said storage-amount sensors; and  
       wherein said controller sequentially stores measurement values measured by said respective concentration sensors and measurement amounts measured by said respective storage-amount sensors, and obtains a change rate of each of the respective measurement values and change rates of the respective measurement amounts, with respect to a predetermined time period;  
       discriminates an ink having a highest change rate among the change rates of other inks, based on combinations of the respective change rates of the toner concentrations and the respective change rates of the amounts of the inks which are stored in the respective storage tanks; and  
       controls the toner concentration of the discriminated ink and the amount of the discriminated ink.  
     
     
       4. A liquid developing device comprising: 
       a storage tank which stores an ink, including a toner and a carrier, for developing an electrostatic latent image formed on a photoconductor;  
       an ink supply pump which sends an ink from said storage tank to the photoconductor;  
       a concentration sensor which measures a toner concentration of the ink to be sent to the photoconductor;  
       a storage-amount sensor which measures an amount of ink stored in said storage tank;  
       a concentrated-ink supply pump which sends a concentrated ink from an ink cartridge for storing an concentrated ink to said storage tank;  
       a carrier supply pump which sends a carrier from a carrier cartridge for storing a carrier to said storage tank;  
       an ink discharge pump which discharges excessive ink from said storage tank to a discharge cartridge;  
       a controller which includes a control mode that simultaneously controls and drives said concentrated-ink supply pump, said carrier supply pump, and said ink discharge pump, so as to maintain a predetermined level of the toner concentration of the ink stored in said storage tank and a predetermined amount of the ink, based on a measurement value from said concentration sensor and a measurement amount from said storage-amount sensor; and  
       a photoconductor which is rotated by being driven by a driving roller;  
       a charger which charges said photoconductor with electricity;  
       an exposure device exposes said charged photoconductor to form an electostatic latent image on said photoconductor;  
       a developing unit to which an ink is supplied from said liquid developing device, and which adheres the supplied ink onto a section of said photoconductor which is charged with electricity and on which the electrostatic latent image is formed;  
       a transfer roller which is rotated in synchronization with said photoconductor, and onto whose surface a toner on said photoconductor is transferred so as to transfer the toner onto a recording medium;  
       a fixation roller which is rotated in contact with said transfer roller between which the recording medium is sandwiched, melts the toner transferred onto the transfer roller, and fixes the melted toner onto the recording medium; and  
       a discharge roller which discharges the recording medium onto which the toner is fixed by said fixation roller.  
     
     
       5. A liquid developing method comprising: 
       supplying ink from a storage tank, storing an ink including a toner and a carrier and for use in developing an electrostatic latent image formed on a photoconductor, to said photoconductor;  
       developing said photoconductor with the ink supplied by said supplying;  
       measuring a toner concentration of the ink which is to be sent to said photoconductor by said supplying;  
       measuring an amount of ink stored in said storage tank; and  
       controlling the toner concentration of the ink stored in said storage tank and the amount of the ink, by selectively simultaneously supplying said storage tank with a concentrated ink and with a carrier, and discharging an excessive ink from said storage tank, while developing the photoconductor by said developing, based on a measurement value measured by said measuring the toner concentration and a measurement amount measured by said measuring the amount; and  
       wherein said controlling includes supplying a concentrated ink to said storage tank, supplying a carrier to said storage tank, and discharging an excessive ink from said storage tank, based on an error between the measurement value and a predetermined value of a toner concentration and an error between the measurement amount and a predetermined amount of ink, so as to approach the toner concentration of the ink stored in said storage tank and the amount of the stored ink to the predetermined value and the predetermined amount, respectively.  
     
     
       6. The liquid developing method according to  claim 5 , wherein said controlling includes 
       supplying a concentrated ink to said storage tank, supplying a carrier to said storage tank, and discharging an excessive ink from said storage tank, so as to supply said storage tank with an amount of an ink or carrier, in accordance with at least one of the error between the measurement value and the predetermined value of the toner concentration, an integrated result of the error, and a differentiated result of the error, and to supply to or discharge from said storage tank an amount of a liquid, in accordance with at least one of an error between the measurement amount and the predetermined amount of the ink, an integrated result of the error, and a differentiated result of the error.  
     
     
       7. A liquid developing method comprising: 
       supplying four kinds of inks, each of which includes a toner and a carrier, for use in developing an electrostatic latent image formed on a photoconductor, respectively from four storage tanks to the photoconductor;  
       developing the photoconductor with each of the four inks which are supplied by said supplying;  
       measuring a toner concentration of each of the inks to be supplied to the photoconductor by said supplying;  
       measuring an amount of each of the four inks included respectively in the storage tanks;  
       controlling the toner concentration of each of the four inks stored respectively in the storage tanks and the amount of each of the four inks, by supplementing each of the storage tanks with a concentrated ink and a carrier, and by discharging an excessive ink from each of the storage tanks, while developing the photoconductor by said developing, based on the measurement value measured by said measuring the toner concentration and the measurement amount measured by said measuring the amount;  
       wherein said controlling step includes:  
       sequentially storing the measurement values which are measured by said measuring the toner concentration and the measurement values which are measured by said measuring the amount;  
       obtaining a change rate, with respect to a predetermined time period, of each of the measurement values sequentially stored by said storing;  
       discriminating an ink having a highest change rate among the change rates of other inks, based on combinations of the respective change rates of the toner concentrations and the respective change rates of the amounts of the inks which are stored in the respective storage tanks; and  
       controlling the toner concentration of the discriminated ink and the amount of the discriminated ink.